Now that Great Smoky Mountains RR 2-8-0 1702 is back in operation, does it still have the roller bearing driving axles or converted back to plain bearings? If the latter, were the axles replaced in the process?

From what I understand, I believe they went back to plain bearings. New axles were made, and TVRM assisted in the making of new boxes. I believe I remember reading/hearing that the new boxes use oil instead of the hard grease, like what Strassburg has done on its locomotives.

whodom

Post subject: Re: GSMR 1702 question

Posted: Wed Jan 12, 2005 5:33 pm

Joined: Sun Aug 22, 2004 8:31 amPosts: 1119Location: South Carolina

It definitely was converted back to plain bearings. Based on the info I was given, the sealed Timken bearings that were used failed after a relatively short life.

The roller bearings used were not the traditional design bearings that had been typically used on steamers, but were an attempt at adapting current off-the-shelf Timken sealed railroad bearings for use on a steamer. The main reason traditional roller bearings couldn't be used is lack of sufficient room in the frame openings. These were sized for friction bearings, which typically require significantly less diametrical clearance than roller bearings. Even with the relatively small diameter roller bearings used, the axles had to be turned down to fit the bearings. Then, bushings were pressed onto the ends of the axles to restore the original diameter and the drivers were pressed back on. The original driving boxes were modified to accept the roller bearings and had to be replaced when the reversion to friction bearings was carried out.

There seem to be several theories as to what the ultimate cause of the failure was (grease lubrication vice oil, lack of proper bearing boxes to hold both rollers on each axle in alignment, excessive stress due to curvy railway, etc.). Railway management was understandably unwilling to pursue this R&D effort; hence the conversion back to conventional bearings.

I sure hate to see such an expensive attempt at modernizing a steamer fail.

The 1702 was converted back to friction bearings. The decision to go back to friction bearings was the same as the initial reason for doing the conversion. Lower maintenance costs. Unfortunitly, when you do an experiment you are not always presented with the data that you are looking for. In this case, for the five seasons that the rollers were under the loco, there was little to no maintenance. But the cost of replacing them in conjuction with the abrieviated life span made retrofitting the loco the best decision.

The axle and box design was very much based on a sister S-160 #611 (currently at TVRM). I went back with oil cellars instead of grease because of the greater availabilty of oils and the ease of maintenance. I use Journaltex HD 57 from Texico. We made the crown brass out of a hi-lead bronze, with some interesting but simple oil grooves. The cellars have a 6x11 journal pad to move the oil. We run the loco between 15 and 20mph, and have consistantly arrived in Bryson City (16 miles) with axle/box temperatures 5-10 degrees above ambient, if that. Number four is a little warmer, but it's a Consolidation. The rod bearings are also made of hi-lead bronze and run about the same. All of the major machining and design work was completed by Steam Operations Corporation, and the other wheel work and crankpin work was completed by TVRM. Both know their business and are great to work with. The 1702 was also fitted with hub liners that can be replaced without anything more than an N-wrench. 2-3 hours and it's out with restored lateral. Give Scott Lindsay a call if your interested in the idea.

Unfortunitly, we are not having the same luck with the boiler as we have with the running gear. A press release is forth coming, but the 1702 is currenty stripped for a 1472, and will be recieving an improptu new firebox. (Yes, all the inner sheets). It will likely not be in service this coming season. Rumer is that sometimes one can get through a winter by only doing an annual on one of these things!!!

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